Equilibrium in the Reactive Extraction of Aqueous Phenol Using Tributyl Phospate in n-Hexane
Abstract
Phenol is a hazardous chemical which usually contained in the wastewater from some industries, such as oil refineries, coal processing, and plastics. Phenol is dangerous substance to a microorganism although in low concentration in wastewater. According to the United State Environmental Protection Agency, the maximum concentration of phenol in wastewater is 1 ppm. This requirement is lower than the concentration of phenol in normal wastewater discharged from industries that is 100 to 1000 ppm. Phenolic substances are very difficult to be destroyed by oxidation in the present of microorganism. Chemical oxidation of phenolic substance using ozone or combination between the ozone and UV irradiation is impossible to handle huge amount of wastewater due to the expensiveness of ozone production and also its low solubility in water. The prospective method to recover of phenol from wastewater is reactive extraction in which phenol makes a complex with the extractant. This research investigated the equilibrium of the reactive extraction of phenol from water using tributyl phosphate (TBP) in n-hexane. An equilibrium model has been developed in this research and the laboratory experiments have been carried out. The parameters of the laboratory experiment are the initial concentration of TBP in n-hexane, and the extraction temperature. The experimental results showed that the higher the TBP concentration in n-hexane, the higher the amount of phenol which can be extracted to the organic phase. The correlation between the distribution coefficients (Kc) with the ration of TBP concentration (CoTBP) to the initial TBP concentration (CoiTBP) in n-hexane can be formulated by Kc=11.59-12.002(CoTBP)/(CoiTBP) with the sum of square of error of 10.87%. The lower the extraction temperature, the higher the amount of phenol extracted to the organic phase. The correlation between the distribution coefficients with the temperature (T) can be approached by Kc=1505.45(1/T)-4.06 with the sum of square of error of 2.63%. The value of distribution coefficient of physical equilibrium (Kp) decreases with the increase of temperature, meanwhile the value of the equilibrium constant of solvation reaction (Kr) is increase with increasing the temperature. The expression of Kr as a function of temperature is Kr=-2.8636(1/T)+0.0133 with the sum of square of error of 0.04%.
References
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